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John Loser (jloser)

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Posted on Monday, September 16, 2002 - 07:32 am:   Edit Post

I have been in the professional/commercial audio installation field for more than 21 years. I have designed systems for houses of worship, schools, audioriua and other venues for more than 17 years. I believe I have the "bone fide" to make this rather blunt comment.

Any Radio Shack distributor is completely unqualified to propose or bid an installed sound reinforcement solution for a performance venue or house of worship. Radio Shack is a consumer-oriented store; that is their mindset. The company does not train its employees in the methods of determining true needs of a performance venue or house of worship nor in the proper methods of designing and implementing solutions to meet those needs.


John Loser
Audio101 Consultants
jloser@audio101.net
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Tom Hansen (tom)

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Posted on Sunday, September 15, 2002 - 10:45 pm:   Edit Post

Hello,
I want to thank everyone for their input and time with helping me out. I have sure learned alot about speaker systems, and the quality of the product and the craftsmanship of the installing technician. I will share this info with the other church members.

Yes it was a bogen model gs 1000, that was in the radio shack bid.

Thank you again.

Tom
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Robert Warren (robertwarren)

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Posted on Saturday, September 14, 2002 - 11:12 am:   Edit Post

I'm normally not a fan of Peavey, however for a cheaper 70v amp there stuff is pretty good. A lot better than the Bogen. If you want really good quality check out the Crown Com-tech stuff, the Com-tech 410 is a great 70v amp.

As far as Tom's question goes,
I would not use 70v for my main system unless it was an unusual circumstance. ( like a flat ceiling around 10-12 feet high and the church did not want to see any speakers )
It's fairly standard for use in:
Over balcony
Under balcony
Hallways
Bathrooms
Nursery/offices

Under balcony/Over balcony - just depends on how many speakers are needed and how far the seats are from the ceiling above the seats you're covering. A lot of times 8 ohm speakers are still preferred for this.

Rob
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Samuel Lin (samlin7)

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Posted on Friday, September 13, 2002 - 08:13 am:   Edit Post

I installed a 70V system as a distributed sytem throughout the church. I work ok for speech only applications. I installed a Bogen amp, and I can tell you one problem I had. The fuse kept popping, something was tripping it. I called bogen up and they asked what was going into the amp, and I said the a signal from my mixer. They stated that it can only handle .5 V of input coming in. I though that was silly, only mic level signal can go in. So I just lowered the output volume from my mixer to below unity which is about exactly .5V.

Well what I am trying to say here is that my experience in a 70V is 2-fold, 1) don't by a bogen amp (though they do have some good products) and 2)the next 70V system I purchase, I will make sure it can handle line level signals inputs
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John Loser (jloser)

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Posted on Friday, September 13, 2002 - 07:31 am:   Edit Post

Tom asked:
"What is a foh system?"

F.O.H. stands for "Front of House". This is the main sound reinforcement system for a house of worship, an auditorium, or any performance venue. The FOH got its name because the speakers are in the front of the house (the audience area), as opposed to stage monitors or backstage program monitors.

I hope this helps.

John Loser
jloser@audio101.net
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John Loser (jloser)

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Posted on Friday, September 13, 2002 - 07:24 am:   Edit Post

Tom,
You asked how high the speaker should be installed in your church. The best answer is, "it depends."
You describe your church as being 40x100 with 15' side walls, but do not describe the height of the peak. For anyone to attempt to describe "how high the speaker should be, we need that information and more. For instance, how deep is the platform?How far is it from the front of the platform to the first row of pews? How are the pews configured? (I might presume that they are two rows of pews, about 13' wide, with a center aisle of 6 feet width and two side aisles of 4'.)
What is the construction? is the floor carpeted? Are the pews padded?
These are the questions (and more) that a good consultant would ask in order to provide the best answers.
If you would like to discuss this, please feel free to write me off list. I am in Michigan.

John Loser
jloser@audio101.net
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Walter Pearce (walter)

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Posted on Friday, September 13, 2002 - 12:58 am:   Edit Post

Tom, IMHO Radio Shack gear in the main is only 'entry level' equipment but may be good enough if you only require speech amplification and you are on a limited budget.

If you plan to move towards more contemporary worship with singers and musicians you will need adequate speakers and power amplifiers to match, plus a mixing desk.

A central speaker cluster positioned high up, angled down into the congregation and slightly forward of the pulpit usually provides the best coverage.

I suggest you read a primer on church sound that addresses most of these issues at http://www.echurch.com/sound/training.html

Also look at the Audio Systems Group website http://www.audiosystemsgroup.com/3Times.pdf article on how to buy the right system that will serve your churches needs in the long term.

If you want more help you can contact me off list at sound@today.com.au

Walter
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Tom Hansen (tom)

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Posted on Thursday, September 12, 2002 - 11:57 pm:   Edit Post

one more question.

what is a foh system?
I have read some of the Q and A posts, very interesting, I sure have learned alot.

Thanks
Tom
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Tom Hansen (tom)

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Posted on Thursday, September 12, 2002 - 11:53 pm:   Edit Post

Thanks alot walter.

One of the systems we have a bid from is radio shack. using a 70 volt system. Please comment if you have any experience with them. Is it a good brand?

This is a small old church, 40 x 100. The side walls go about 15' straight up and then angles in to the center peak. how high should the speakers be?

Thank you for any help.
tom
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Walter Pearce (walter)

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Posted on Thursday, September 12, 2002 - 11:01 pm:   Edit Post

Hi Tom, welcome to the list.

70v line is traditionally used with distributed speaker systems where there are a number of speakers located over a wide area. (Foyers, kitchens, chreche/cry rooms etc)

Transformers with adjustable taps are typically mounted on the rear of the speaker frame so that a suitable sound pressure level is achieved. (IE: A noisy area will require more SPL)

Line transformers will exhibit some power loss, affect the frequency response of the system and provide a more difficult load for the power amplifier to drive.

Older halls and churches may still have legacy FOH systems installed using 70v line, column speakers etc - These are only suitable for speech reproduction.

For a front of house system 8 ohms is the norm. The only exception being long rooms with low ceiling height where a distributed system is often a better alternative.

Walter
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Tom Hansen (tom)

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Posted on Wednesday, September 11, 2002 - 10:23 pm:   Edit Post

Hello.
I am also looking into a sound system for my church. Which is better a 70 volt or a 8 ohm system? thank you.

Tom
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Walter Pearce (walter)

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Posted on Thursday, July 11, 2002 - 10:17 pm:   Edit Post

Sam, you can use metal conduit if you wish, but in my opinion this is overkill unless your church is located near a high powered radio/TV transmitter or other strong source of RF. Plastic pipe with twisted pair inside is normally quite OK. I spent 35yrs working in Telecommunications & Broadcasting so I can speak with some authority.

You can buy a couple of spools of single insulated electrical wire from an electrical supply house and make up your own using a power drill to twist the wires. Cut the wire about 20% longer than you need as twisting will effectively shorten the pair. As Blake mentioned, don't skimp on copper - long cable runs or high powered installations require larger conductor sizes to avoid power loss.

Rather than running duct around the walls as mentioned in your other post why don't you just run ALL the cables under the floor - much quicker and neater in my opinion.
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Blake A. Engel (blakeengel)

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Posted on Wednesday, July 10, 2002 - 12:52 pm:   Edit Post

Sam,

You can buy 1-pair twisted cable just about anywhere. It's not uncommon. There are many companies that make it; just look for twisted speaker cable. Be sure to get a large enough cable; don't skimp on the copper! :-)

Blake Engel
All Church Sound
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Samuel Lin (samlin7)

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Posted on Wednesday, July 10, 2002 - 11:31 am:   Edit Post

Thanks Blake
For some reason I didn't think just twisting 16 guage cables was the answer. Any suggestions on where I can pick up cables like that, or do I need to actually buy these cables and twist them myself? Do they come twisted already.

Regarding the iron conduit, do you need to ground it?
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Blake A. Engel (blakeengel)

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Posted on Wednesday, July 10, 2002 - 11:12 am:   Edit Post

Not to butt in, but Sam asked if he could just twist his two monitor sends....

That's really not the idea--the idea is that the two conductors in each circuit should be twisted. Therefore, you should not use ordinary zip cable (lamp cord) or plain old THHN wire used to wire electrical outlets. You CAN use THHN if you first twist the two conductors.

Basically, the twisting helps a lot in reducing noise that can be picked up by the cable. In normal mic level and line level connections, the shield isn't the critical link; it's the twisted cable. The telephone company runs balanced connections thousands of feet with no problems (and no shield!). The twist is most important.

Why does it matter if the speaker output lines are twisted? This has been talked about before on this forum, but basically the output stage of an amplifier has what's called a 'feedback loop'. Essentially a portion of the output of the amplifier is fed back into the input. Now, once you connect a length of cable to the output of your amplifier, it becomes an antenna. The speaker on the other end won't ever let you hear what the antenna is picking up (since the RF signals are so low). BUT! BUT! the RF signals can travel back to the amplifier-through the feedback loop circuit, and become audible once they become unmodulated and are amplified through the amp circuit.

Sometimes this results in radio stations or other strange noise, other times it isn't audible because it's a very high frequency.

The other issue is with running speaker level lines near mic level lines. Anytime you have current flowing through a wire, there's a magnetic field produced around that wire. That magnetic field around the speaker line can be induced into the mic line(s). This signal then gets back to the mixer and other processors, and back out the amp and down the speaker line. This all occurs very quickly, resulting in a magnetically induced feedback loop. This may be at an audible frequency, ubt is usually at a very high frequency that you don't hear. After a while, you amp is running real hot and you keep blowing HF drivers.

While many people have never seen this happen, and while even I have run high level speaker and monitor cables right next to mic lines (temporary), I've not always had trouble with it. It's sort of a "it depends" issue; but why risk it?!

Finally, PVC does nothing when it comes to adding shielding to any cables. It can only provide physical protection and an easy pull path. If you want good protection, you need to install iron conduit (not thinwall).

Blake Engel
All Church Sound
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Samuel Lin (samlin7)

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Posted on Wednesday, July 10, 2002 - 10:28 am:   Edit Post

Thanks Walter
That was sounds like some good advise, will be doing that. SO do you mean if I had two cables going to my floor monitors I should just twist the the 2 cables? -Just making sure.

SAM
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Walter Pearce (walter)

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Posted on Wednesday, July 10, 2002 - 09:26 am:   Edit Post

Samuel, parallel runs of microphone and speaker lines are OK for short distances when balanced microphone cable is used, but it is always good practice to seperate them where possible.

Running speaker cables via the snake is HIGHLY INADVISABLE for the following reasons:

A> Due to the large signal levels on the speaker line being in close proximity to low level microphone inputs. This has potential to create system oscillation due to the 90dB or so signal differential between the two circuits.

B> The small gauge wire used in the snake having higher resistance compared to normal speaker cable. This will cause excessive power loss between amplifier and speaker, and secondly it will degrade the damping factor resulting in soggy bass.

I recommend that you run the speaker cables via the PVC pipe under the floor and keep the snake at least 6-12" away. The speaker lines will exhibit lower crosstalk if they are twisted throughout the length of the run. (Some installers run the speaker lines in metal pipe and ground it at one end to further improve the crosstalk figures)

Good luck with your installation...

Walter
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Samuel Lin (samlin7)

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Posted on Tuesday, July 09, 2002 - 11:59 pm:   Edit Post

Hi all
I am installing a sound system in myc church. I remember reading somewhere that speaker level signals are not be be parallel with line or mic level signals. Is that true? If so what is the minimal distnace they would need to be separated? And would it be advisable to run the speaker-level cables through a PVC pipe under my floor near my snake? Or is there something else like a PVC pipe that would work better in isolation of the signal. Well if that statement is not true (speaker level signals are not be be parallel with line or mic level signals) Then can I run the speaker level signal through my snake (from the amplifer to the floor monitors) along with my mic level signals?
Thanks

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